The present invention relates to housings for electronic equipment, and is particularly concerned with improving the electromagnetic shielding properties of cages or mounts for detachably mounting ancillary compartments such as disc drives in such housings.
In order to improve serviceability of electronic equipment using hard disc drives, it is conventional to mount the hard disc drive so that it is easily removable from the equipment. This is conventionally done by providing the hard disc drive with a pair of runners extending along opposite side surfaces of the hard disc drive unit, and providing in the equipment housing a cage to receive the hard disc drive unit wherein side faces of the cage are provided with slots into which the runners may be received and guided during insertion and removal of the hard disc drive from the cage.
The presence of these necessarily elongated slots in the sides of the hard disc drive cage significantly reduces the efficacy of the cage in respect of its electromagnetic shielding properties. The correlation between the frequencies which can pass through an opening in an electromagnetic shielding plate and the maximum dimension of that opening are such that, when elongated slots are provided in the hard disc drive cage, significant escapes of electromagnetic energy can take place through these slots.
When a hard disc drive is in place in the cage, the casing of the hard disc drive itself may go some way to closing the gap in the electromagnetic shielding, but when the disc drive is removed a significant gap in the electromagnetic shielding for the components within the circuit housing is opened.
An aspect of the present invention seeks to provide a hard disc drive cage with enhanced electromagnetic shielding. This aspect provides a component cage for detachably mounting an auxiliary component in a housing of an electronic circuit, wherein the component comprises a pair of supporting runners, the cage being formed from electromagnetic screening material and comprising:
an open front face;
a pair of parallel spaced sidewalls extending perpendicularly to the open front face;
a rear face extending between the sidewalls at their ends remote from the open face; and
a transverse wall extending between the sidewalls perpendicularly to the plane of the open face, wherein the sidewalls are substantially continuous and are provided on their internal surfaces with a step surface for engaging a respective supporting runner of the component, the step surfaces extending in a plane parallel to the transverse wall and spaced therefrom.
A second aspect provides a circuit housing having a disc drive cage, and a third aspect provides a modular rack-mounted circuit having modules including the cage.